Fluorocarbons (CFCs) have conventionally been the main refrigerant used in refrigeration devices; however, developments have been made over the past several years in regard to technologies in which carbon dioxide is used as a refrigerant. Carbon dioxide refrigeration cycles, such as disclosed in Japanese Laid-open Patent Publication No. 2001-74342, are widely known in the field of air conditioners used in automotive vehicles, and commercial products in which carbon dioxide is used as a refrigerant are used in the field of hot-water-supplying devices.
However, products used in the field of air conditioners for domestic or office use are currently only in the developmental stage, and are not yet ready to be brought to market.